This invention pertains to wheel balancing systems and machines and more particularly to such a system having means for selectively modifying input data measured in a manner pertinent to one style of wheel to cause the data to be pertinent to another style of wheel.
In known machines for balancing vehicles wheels balance equations are solved based on known input data. Such data includes, among other things, the radius or diameter of the rotational path of weights attached to the wheel as well as the spacing between parallel planes defined by and including the rotational paths of the inner and outer weights. Since wheel weights are typically clipped to the edge of the inner and outer rims, the diameter of the rotating paths corresponds substantially to the wheel diameter. Also, the spacing between the planes defined by the rotating weights corresponds substantially to the spacing between the rims. Thus, the above data as to diameter of the path of each weight as well as the spacing between the planes thereof can be easily obtained by an operator by merely noting the stated wheel diameter and by measuring the distance between the rims using calipers or other means.
The above correlation between the location of the weights and rim diameter and spacing does not pertain to certain popular styles of wheels, such as wire spoke wheels or aluminum alloy wheels (all referred to hereinafter as "mag" wheels) since the weights are not clipped to the edge of the rims. Thus, entry of data by following the above simple procedure based on indicated wheel diameter and measured spacing between rims would provide incorrect results. Thus, another balancing procedure has had to be employed for wheels (such as "mag" wheels) where the weights are not carried by the edge of the rims.
Thus, in the past, the balancing of "mag" wheels has required the operator to attempt to measure the actual spacing between the planes defined by rotational movement of the weights as well as to estimate the radii of the rotational paths of each weight to provide data for the system. By imposing different measuring and information collecting procedures upon the operator based upon balancing of conventional steel wheels or "mag" wheels, the chances for entry of erroneous data is believed to be significantly increased.
The system as disclosed herein permits the operator to pursue the same routine for "mag" wheels as is pursued for steel wheels except that when balancing "mag" wheels a control element is initially activated to operate means for converting readings taken in a manner as though the wheel were a standard wheel to data pertaining to "mag" wheels.
It has been observed that the mounting of certain minimal amounts of weight to a wheel for purposes of attempting to balance the wheel may be substantially ineffective for most practical purposes. Accordingly, means have been provided according to one embodiment herein for displaying zero weight when, in fact, an amount of weight below a given minimum may actually have been calculated by the balancing system. Accordingly, means are provided for blanking out these sub-minimum weight values as a matter of convenience by displaying zero weight instead. According to one embodiment of the invention means are provided for selectively establishing one of a plurality of minimum weight levels based on the magnitude of one of the input parameters inasmuch as the value of minimum weight will vary with the value of at least one of the input parameters to the system.
As noted above, in balancing a "mag" wheel with the system as disclosed herein a control element may be initially activated in order to operate means for modifying the values of readings taken in a manner as though the wheel were a standard steel wheel so that the input information for mag wheels can be obtained from the same locations as the wheel as used for standard steel wheels. The foregoing style of system is rendered possible by virtue of the fact that a substantial majority of "mag" wheels have substantially the same characteristics. However, there are additional classes of "mag" wheels which do not conform to the characteristics of the majority and, accordingly, in accordance with another embodiment of the invention, means are provided for selectively modifying the input information in accordance with one of a plurality of different classes of "mag" wheels.
Typically, weights applied to a "mag" wheel are disposed more closely together and are arranged to travel rotationally in paths having mutually different diameters each less than that of weights employed on standard steel wheels. As shown in FIG. 2 conventional wheel weights 16 are shown in phanthom lines positioned at the edge of the inner and outer rims of a "mag" wheel. The foregoing attachment, as is known, is unsatisfactory. Accordingly, a different style of weight is employed which is adhesively attached to the surface of the wheel in a position as closely approximating that of wheel weights 16 as possible but without being exposed to view from a position located at the side of a vehicle having such wheels. Thus, both weights are usually disposed on the back side of the "mag" wheels, i.e. the inner side, so as not to affect the appearance of the wheel.
As shown in FIG. 2, inner and outer "mag" wheel weights 17, 18 are shown in position. From inspection of FIG. 2 it is evident that the spacing 19 normally established for conventional wheel weights 16 is substantially greater than the spacing 21 between wheel weights 17, 18. In addition, the diameter 22 of the rotational path of weight 17 and diameter 23 of the path of weight 18 are each less than the path diameter 24 of conventional weights 16. In order to simplify entry of information into the system described herein a mean diameter 26 representing the average between diameters 22 and 23 can be substantially used for both.
Thus, by employing a set of correction factors based on a predetermined relationship between "mag" wheels and related sizes of standard steel wheels, measurement of spacing 19 between the rim edges (and hence substantially between weights 16) can be converted to spacing 21. Also, when using the correction factors, the diameter 24 of the rotational path of a standard weight 16 becomes coverted to the mean diameter 26 for "mag" wheel weights 17.sub.i and 18.sub.o. The "a" dimension will also be modified.
Typical known machines for dynamically balancing vehicle wheels serve to compute an amount of weight to be added to the edge of the inner and outer rims of a wheel. These machines also compute the peripheral location on each rim for locating each weight. In computing the amount of weight to be attached, moments are compared in various known ways and at various times. For illustration, the diagram of FIG. 1 shows certain momentary force conditions for developing a portion of the data to be employed by a balancing machine in solving equations. An example of one type of equation is shown for summing the moments to zero about F.sub.1 and F.sub.2 as in (1) and (2) respectively, below. EQU -F.sub.2 (b-a)+F.sub.3 a+F.sub.4 (a+f)=.phi. (1) EQU F.sub.1 (b-a)+F.sub.3 b+F.sub.4 (b+f)=.phi. (2)
From a consideration of each of these equations it will be evident that physical measurement of the spacing (b-a) between the rims and physical measurement of the "a" dimension, as by means described below, provides all of the variable input data which is necessary for an operator to supply in order to solve each of the above equations. The remaining data remains fixed and is provided by the machine.
Note, for example, that physical measurement of the "a" dimension combined with measurement of the spacing between the rims of a wheel, as by means of calipers or other means serves to provide the "b" dimension. Accordingly, the quantity (b-a) provides a value corresponding to the spacing between the rims of the wheel.
The diagram shown in FIG. 1 represents a known balancing machine provided with a support base 10 with supports 11, 12 extending upwardly to hold a bearing housing 13 thereon. Bearing housing 13 includes a rotatable shaft therein (not shown) supporting a wheel and tire assembly 14 at the right hand end thereof so that the wheel and tire assembly 14 can be rotated by motor means (not shown) coupled to drive the shaft.
As arranged in one construction the movement of bearing housing 13 is limited to a plane normal to the plane of the paper and including the axis of housing 13. Such movement causes sensors s.sub.1 and s.sub.2 carried on supports 11, 12 to be activated so as to provide an indication of the forces F.sub.3, F.sub.4 acting thereon.
The rim diameter, D, constitutes a third entry to be made by the operator based on inspection of the wheel size. Thus, the forces F.sub.3, F.sub.4 are detected by sensors s.sub.1, s.sub.2 respectively. Forces F.sub.1, F.sub.2 can readily be determined by conversion of equations (1) and (2) to the following relations: EQU -F.sub.1 =[F.sub.3 b+F.sub.4 (b+f)]/(b-a) (3) EQU F.sub.2 =[F.sub.3 a+F.sub.4 (a+f)]/(b-a) (4)
The amount of counterbalancing weight to be added to inner rim 14.sub.i and to outer rim 14.sub.o to overcome the forces F.sub.1 to F.sub.2 respectively is known to be inversely proportional to the diameter of the rotational path of such counterbalancing weight and can be represented by equations (5) and (6) where D=the diameter of each rim 14.sub.i, 14.sub.o and K is a constant: EQU Wt.sub.1 =(-F.sub.1 /D).times.K (5) EQU Wt.sub.2 =(-F.sub.2 /D).times.K (6)
Accordingly, the conversion from a determination of forces F.sub.1, F.sub.2 to weights W.sub.1, W.sub.2 to be added to the rims is relatively simply computed.